In the recent development of integrated circuit design, standard cells may include fin field-effect transistors (FinFETs) therein. A FinFET may include a plurality of semiconductor fins, and a gate electrode formed thereon and crossing the plurality of semiconductor fins. Accordingly, the drive current of the FinFET is the sum of the drive currents of the plurality of semiconductor fins.
In conventional design flow of the standard cells comprising FinFETs, design rules are first established. The fin pitch is determined as being equal to the metal pitch of metal lines in a bottom metal layer. Placement and route constraints are also established. Standard cells may then be designed according to the design rules, the fin pitch and the metal pitch, and the placement and route constraints. After the standard cells are designed, the performance of the standard cells is checked. If the performance does not meet the design requirement, the standard cells are re-designed by adding fin numbers and/or adding cell pitch numbers. If the performance meets the design requirement, the gate density of the standard cells is checked against design requirements. If the gate density satisfies the design requirements, the circuit design is ended. Otherwise, a redesign is performed, and the fin numbers of the standard cells may be reduced, and/or the circuit performance target may be lowered.